U.S. patent number 7,283,546 [Application Number 10/452,796] was granted by the patent office on 2007-10-16 for system supporting the dynamic migration of telecommunication subscribers between call services providers.
This patent grant is currently assigned to Ciena Corporation. Invention is credited to John Donak, Jean-Francois Gallant.
United States Patent |
7,283,546 |
Gallant , et al. |
October 16, 2007 |
System supporting the dynamic migration of telecommunication
subscribers between call services providers
Abstract
An access device enables dynamic migration of telecommunications
subscribers between multiple transport networks and call services
providers. The access device stores access patterns that associate
a subscriber with a call server and define trigger events. The
access device monitors the trigger events. The access device
associates the subscriber with a different call server in
accordance with the trigger events and the access patterns. The
trigger events can be dynamic or static, can be on a line-by-line
or call-by-call basis, and can be selected by a user or implemented
by an operator. In this manner, the access device allows graceful
migration of voice services from a legacy network to a
next-generation packet network with lower capital and ownership
costs.
Inventors: |
Gallant; Jean-Francois (Ottawa,
CA), Donak; John (Kanata, CA) |
Assignee: |
Ciena Corporation (Linthicum,
MD)
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Family
ID: |
31954500 |
Appl.
No.: |
10/452,796 |
Filed: |
May 30, 2003 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20040042509 A1 |
Mar 4, 2004 |
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Foreign Application Priority Data
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Aug 30, 2002 [CA] |
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2400548 |
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Current U.S.
Class: |
370/401; 370/352;
370/353; 379/207.02 |
Current CPC
Class: |
H04J
3/12 (20130101); H04L 12/2898 (20130101); H04L
12/6418 (20130101); H04L 2012/6424 (20130101); H04Q
2213/13298 (20130101); H04Q 2213/13381 (20130101) |
Current International
Class: |
H04L
12/28 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Ho; Duc
Attorney, Agent or Firm: Merek, Blackman & Voorhees,
LLC
Claims
The embodiments of the invention in which an exclusive property or
privilege is claimed are defined as follows:
1. An access device in a telecommunications network for coupling
each of a plurality of subscriber loops to any of a plurality of
transport networks, said access device comprising: (a) a plurality
of line termination units for coupling said plurality of subscriber
loops with said access device; (b) a plurality of link adaptors for
coupling said plurality of transport networks with said access
device; (c) a media switch for selectively coupling ones of said
plurality of line termination units with ones of said link
adaptors; and (d) a call control system for controlling said media
switch for determining which of said plurality of line termination
units is coupled with which of said link adaptors and for providing
call control between said plurality of subscriber loops and said
plurality of transport networks associated therewith.
2. An access device as defined in claim 1, wherein said call
control system further includes a memory for storing call service
configuration provided by said access device.
3. An access device as defined in claim 2, wherein said call
service configuration includes descriptions of call control
interfaces that are provisioned and subscriber loop subscription
information.
4. An access device as defined in claim 3, wherein said subscriber
loop subscription information includes a description of an access
pattern specifying transitions between said call control interfaces
and events that trigger said transitions.
5. An access device as defined in claim 4, wherein said call
control system further includes a configuration manager for
managing contents of said memory.
6. An access device as defined in claim 5, wherein said
configuration manager determines which call control interface
provides call services to each of said subscriber loops at any
point in time.
7. An access device as defined in claim 5, wherein said call
control system further includes a provisioning interface for
coupling to a provisioning agent to provide external access to said
configuration manager.
8. An access device as defined in claim 7, wherein said
provisioning interface allows said provisioning agent to define,
modify, remove, enable, and disable call control interfaces and
subscriber loop subscriptions.
9. An access device as defined in claim 5, wherein said call
control system further includes a plurality of network interface
controllers, each of said network interface controllers
corresponding to an associated subscriber loop for controlling said
media switch and providing said call control between said plurality
of subscriber loops and associated call servers.
10. An access device as defined in claim 9, wherein said network
interface controllers watch for, detect and report access triggers
to said configuration manager.
11. An access device as defined in claim 10, wherein said
configuration manager changes said network interface controller
associated with said customer loop upon occurrence of said access
triggers in accordance with said access pattern provisioned for
said customer loop.
12. An access device as defined in claim 9, wherein the call server
is a softswitch.
13. An access device as defined in claim 9, wherein the call server
is a public switched telephone network switch.
14. An access device as defined in claim 9, wherein said call
control system further includes a line supervisor for allocating
and configuring said line termination units and for call control
notifications between said plurality of line termination units and
their associated network interface controller.
15. An access device as defined in claim 1, wherein a bandwidth of
said media switch is greater than an aggregate bandwidth of
connections through said media switch.
16. An access device as defined in claim 1, wherein said call
control is communicated to an associated call server by
multiplexing call control signals with media signals and
transmitting them over a common link.
17. An access device as defined in claim 16, wherein multiple call
control signals are transmitted across a single link.
18. An access device as defined in claim 1, wherein said call
control is communicated to an associated call server by a link
separate from a link transmitting media signals.
19. An access device as defined in claim 18, wherein multiple call
control signals are transmitted across a single link.
20. A method for allowing a subscriber to migrate between services,
said subscriber being coupled with at least one transport network
via an access device, said method comprising the steps of: (a)
storing at said access device an access pattern identifying a
plurality of call servers, one of said call servers for providing
initial service to said subscriber, said access pattern further
defining trigger events; (b) monitoring at said access device for
said trigger events; and (c) transferring control over said
subscriber, upon detection of at least one of said trigger events,
to a different one of said plurality of call servers in accordance
with said detected trigger event and said access pattern.
21. A method as defined in claim 20 wherein different call servers
utilize different transport networks.
22. A method as defined in claim 20, wherein said migration occurs
between calls.
23. A method as defined in claim 22, wherein said subscriber
initiates said migration.
24. A method as defined in claim 22, wherein a system operator
initiates said migration.
25. A method as defined in claim 20, wherein said migration occurs
during calls.
26. A method as defined in claim 25, wherein said subscriber
initiates said migration.
27. A method as defined in claim 25, wherein a system operator
initiates said migration.
28. A method as defined in claim 25, wherein a said migration is
initiated by a predefined event.
Description
The present invention relates generally to telephone network access
technology, and specifically to a system for enabling the dynamic
migration of telecommunications subscribers between multiple
transport networks and call services providers.
BACKGROUND OF THE INVENTION
In a telecommunication system, subscriber lines are generally
connected to a Public Switched Telephone Network (PSTN) via access
network devices. Typically, access devices include channel
interfaces for terminating the subscriber lines and a network
interface for connecting the access device to a local exchange
switch of the PSTN. The PSTN is connected to the network device
using one or more wide-band carrier links. The access device
converts data between an analog signal used on subscriber lines and
a digital signal typically used by the PSTN so data can be
transported over the network. This conversion involves operations
such as sampling and digitizing voice-band signal from each of the
subscriber lines and aggregating the digitized signals from the
plurality of lines into a single signal for transporting, so the
information can be transported more efficiently on the wide-band
carrier links.
Primarily, telecommunication systems have been implemented using
time-division multiplexing (TDM) as the carrier technology of
choice. TDM technology divides the available bandwidth into
timeslots and assigns a predefined timeslot to each subscriber
line. The subscriber line transmits its data to the network during
its assigned timeslot. As such, existing access devices normally
provide a TDM interface to the network in the form of T1 or T3
carrier links. However, as the amount of data traffic travelling
over public packet networks outgrows voice traffic, new access
devices have become available which provide connectivity to
next-generation packet networks, thereby enabling call services to
be provided over a packet network.
However, although a trend is developing towards next-generation
packet network to provide voice communication, there are still many
legacy systems that are reluctant to make such a switch. This
reluctance is because packet network access devices are designed
solely for packet network access. Thus, this limitation has left
service providers with an obligation to keep and maintain legacy
access equipment in parallel with next-generation access equipment,
and follow a costly and inefficient migration path that requires
physically moving subscriber lines from the legacy equipment to the
packet-network access device. This difficulty discourages service
providers from adopting next-generation packet networks, thereby
delaying the introduction of new call services that a packet-based
infrastructure would make possible.
Therefore, it is an object of the present invention to obviate or
mitigate at least some of the above-mentioned disadvantages.
SUMMARY OF THE INVENTION
It is an advantage of the present invention that a single access
device provides access to multiple transport networks and allows
subscribers to migrate between transport networks on a line-by-line
basis. Further, the convergence of multiple transport network
technologies into a single access device presents opportunities for
new services that require the capability to change the association
between a subscriber line and call services provider on a
call-by-call basis or even in mid-call. One such service
automatically routes data modem calls over the packet network to
reduce the load on the TDM network. Another service allows
subscribers to switch to a different call service provider to take
advantage of lower rates. Yet another service automatically
switches a subscriber line to a different transport network upon
failure or congestion of their usual network. Such service
opportunities abound and can be facilitated by the invention, as
will be appreciated by a person skilled in the art.
In accordance with an aspect of the present invention, there is
provided an access device in a telecommunications network for
coupling each of a plurality of subscriber loops to any of a
plurality of transport networks. The access device comprises the
following components. A plurality of line termination units couple
the plurality of subscriber loops with the access device. A
plurality of link adaptors couple the plurality of transport
networks with the access device. A media switch selectively couples
ones of the plurality of line termination units with ones of the
link adaptors. A call control system controls the media switch for
determining which of the plurality of line termination units is
coupled with which of the link adaptors and for providing call
control between the plurality of subscriber loops and their
associated transport networks.
In accordance with yet a further aspect of the present invention,
there is provided a method for allowing a subscriber to migrate
between services, the subscriber being coupled with at least one
transport network via an access device, the method comprising the
steps of: storing at the access device an access pattern
identifying a plurality of call servers, one of the call servers
for providing initial service to the subscriber, the access pattern
further defining trigger events; monitoring at the access device
for the trigger events; and transferring control over the
subscriber, upon detection of at least one of the trigger events,
to a different one of the plurality of call servers in accordance
with the detected trigger event and the access pattern.
BRIEF DESCRIPTION OF THE DRAWINGS
An embodiment of the invention will now be described by way of
example only with reference to the following drawings in which:
FIG. 1 is a block diagram of a network having an access device with
multiple network interfaces;
FIG. 2 is a detailed block diagram of the access device illustrated
in FIG. 1; and
FIG. 3 is a flow chart illustrating the operation of the access
device.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
For convenience, like numerals in the description refer to like
structures in the drawings. Referring to FIG. 1, a
telecommunication network is illustrated generally by numeral 100.
The network 100 comprises a plurality of subscriber devices, or
endpoints 102, an access device 104, a local exchange 106, a Public
Switched Telephone Network (PSTN) 108, a packet network 110, a call
server 112, an internet service provider (ISP) 114, the Internet
116, a directory server 118, a content server 120, and a
conferencing server 122.
The endpoints 102 include Plain Old Telephone Service (POTS)
devices, various formats of Digital Subscriber Loop (xDSL) devices,
and wireless devices such as cellular telephones, personal digital
assistants (PDAs), and notebook computers. The endpoints are
coupled to an access device 104 in accordance with the type of
endpoint. For example, POTS and xDSL devices are coupled to the
access device 104 via a copper twisted-pair and wireless devices
are coupled to the access device 104 via a wireless network. Such
connections are known in the art and need not be described in
detail. The access device 104 is coupled to the local exchange 106
via TDM links 105. The local exchange is, in turn, coupled to the
PSTN 108. The access device 104 is further coupled to the packet
network 110 via packet links 109. The packet network is coupled
with the call server 112, conferencing server 122, ISP 114,
directory server 118, content server 120, and the like as will be
appreciated by a person skilled in the art. The ISP 114 is further
coupled to the Internet 116, or other wide area network.
The access device 104 is capable of supporting multiple signaling
protocols, which in the present embodiment includes both PSTN and
packet network signals. This architecture allows subscribers to
receive call services from the legacy PSTN network 108,
concurrently with other subscribers on the same access device 104
receiving enhanced call services from the next-generation packet
network 110. Interfaces on the access device 104 allow a service
administrator to dynamically assign subscriber lines on a
line-by-line basis to any available network, using the same access
device.
Thus, the architecture enables the graceful migration of voice
services from the legacy PSTN 108 to the next-generation packet
network 110, which translates into multiple benefits for a service
provider as well as a service subscriber. The architecture reduces
capital and ownership costs of the access equipment, as this
configuration reduces the need to retain and maintain dedicated
legacy access equipment. Risks associated with the introduction of
new enhanced voice services using packet network technology are
reduced, as new services can initially be offered as a trial to
small groups of customers and later deployed to a larger customer
base. Further, early technology adopters can subscribe to enhanced
services as they become available, thereby creating new revenue
streams for the network operator, without the cost of an "all or
nothing" migration of subscribers to the next generation network
110 as would occur if the operator had to purchase separate TDM and
packet access devices.
Referring to FIG. 2, a more detailed diagram of the access device
104 is illustrated. The access device includes a plurality of line
termination units 202, a media switch 204, a call control system
206, and a plurality of link adapters 208. The line termination
units 202 terminate the signals from the endpoints 102, as is
common in the art. The line termination units 202 are each coupled
to the media switch 204. The media switch 204 is coupled to each of
the link adapters 208. Each of the links adapters is coupled to a
corresponding transport network 210.
The call control system 206 includes a line supervisor 212, a call
services configuration repository 214, a configuration manager 216,
and a plurality of network interface controllers 218, each of which
may be implemented as a combination of hardware, firmware or
software components. The line supervisor 212 is coupled to each of
the line termination units 202 via an endpoint control interface
211. The line supervisor 212 is further coupled to each of the
network interface controllers 218 via a line control interface 213.
Each network interface controller 218 is coupled with the media
switch 204 and the configuration manager 216 via a switch control
interface 219 and an access control interface 217, respectively.
Each network interface controller 218 is further coupled to a
corresponding call server 222 via a call control interface 223. The
configuration manager 216 is further coupled to the call services
configuration repository 214 and a provisioning agent 220 via a
repository interface 215 and a management interface 221,
respectively.
The access device 104 has carrier links 209 to each of the
transport networks 210. Each carrier link physically terminates at
the link adapter 208 in the access device 104. The link adapters
208 transmit and receive signals and media streams between the
access device 104 and the transport networks 110, performing a
layer-2 adaptation between the media switch 204 and the carrier
links 209. The link adapters 208 use different carrier
technologies, including time-division multiplexing (TDM),
asynchronous transfer mode (ATM), synchronous optical network
(SONET), Ethernet, and the like, depending on the transport network
to which it is connected, as will be appreciated by a person
skilled in the art.
The line terminations units 202 comprise hardware, firmware and
software elements for providing the physical interface to the
endpoints 102. A line, in the present context, comprises a
communications path to individual endpoint equipment over which
media and control signals are received and transmitted. Each line
may consist of a separate physical link between the endpoint
equipment 102 and the access device 104. Alternatively, lines from
multiple endpoints may be aggregated in front of the access device
104, and then transported over a multiplexed link to the access
device. In the latter case, the lines are de-multiplexed before
they are fed to their respective line terminations units 202.
The line terminations units 202 further include signal processing
resources and functions required for coupling the endpoints 102
with the supported networks 210 and carrying the media stream
across the media switch 204. These signal processing resources
include analog/digital converters, payload encoders/decoders,
packetizers, jitter buffers, echo cancellers, tone detectors, tone
generators, modems, and the like.
The media switch 204 provides connectivity between the line
termination units 202 and the link adaptor 208 for accessing the
carrier links 209 to the networks 210. The media switch is able to
establish a media stream connection between any line termination
unit 202 and any carrier link adapter 208, and supports multiple
simultaneous connections. The media switch 204 selectively couples
each of the line termination units 102 with a corresponding link
adapter 208 in accordance with the configuration of the call
control system 206. Thus, the call control system 206 determines
the destination for each endpoint on a line-by-line basis. The
details of the media switch are known in the art and, thus, need
not be described in detail. Any appropriate switching technology,
be it standard or proprietary, may be used. ATM and IP are two
examples of standard switching technologies that may be used. In an
IP switch, priority routing is based on the quality of service
attributes of each packet, and packets of equal priority are routed
on a First Come/First Served basis. In ATM, routing is based on the
traffic descriptor of each virtual circuit through the switch, and
ATM cells from circuits of equal priority are routed on a First
Come/First Served basis. Switching quality degrades if the
aggregate bandwidth of active connections exceeds the bandwidth of
the switch.
Each carrier link 209 is used to transport media streams to and
from the access device 104. The same carrier links are typically
used to transport call control signals to the call servers 222, in
which case the call control signals are multiplexed with the media
streams. Alternatively, separate carrier links may be dedicated to
the transport of call control signals. For clarity the call control
interfaces illustrated in FIG. 2 are shown to be separate from the
carrier links 209. Further, because call control interfaces are
logically independent from transport networks, it is possible for
multiple call servers to use the same transport network to provide
their call services. Thus, a transport network 210 may carry
control signaling from multiple call servers 222 to the same access
device 104.
The call server 222 is a network entity that provides control logic
and signaling for establishing media paths between endpoints. In
conventional telephony networks, call servers are typically
responsible for administration functions such as call traffic
measurement and billing. Examples of call servers include
conventional local exchange PSTN switches as well as
next-generation call controllers, referred to as softswitches.
The call server 222 determines a call control protocol to be used
at its interface 223 with the access device 104. Conventional local
exchange switches, which use TDM carrier links, use control
protocols including SS7, TR-08 or GR-303, and the like.
Next-generation packet-based call servers use peer signaling
protocols including H.323, SIP, master-slave control protocols such
as MGCP and MEGACO/H.248, and the like.
The design of the interfaces between components in the call control
system is such that it allows the components to be physically
contained in separate units. Thus the call control system can be
implemented as a single device, or it can be implemented as a
distributed access device, wherein the units are interconnected by
intervening communication links or networks.
Referring to FIG. 3, a flow chart illustrating the general
functionality of the access circuit is illustrated generally by
numeral 300. At step 302, the access device stores an access
pattern identifying a plurality of call servers. The access pattern
further defines trigger events for each of the subscribers and each
of the transport networks. One of the call servers provides initial
service to the subscriber. At step 304, the access device monitors
incoming signals for identifying the trigger events. If one the
trigger events is detected, at step 306 control over the subscriber
is transferred from the current call server to a different call
servers in accordance with said detected trigger event and said
access pattern, thus providing the migration as desired.
The functionality of the call control system is described in detail
below. The call services configuration repository 214 provides
persistent storage for descriptions of provisioned call control
interfaces 223, and endpoint subscription information. Each call
control interface description provides the network coordinates of
an associated call server 222, a set of carrier links 209 to use
for the call services offered by this server, and the parameters of
the call control protocol to use on this interface. The
subscription information for an endpoint specifies an access
pattern which identifies the call server or plurality of call
servers that are capable of providing service to the endpoint. The
access pattern indicates which of the call servers 222 initially
provides service to the endpoint, and defines events that, when
they occur, trigger a transition to a different call server. An
endpoint may be left in an unprovisioned state, where it does not
subscribe to any call service.
The configuration manager 216 maintains the contents of the
repository 214 and provides an interface 221 for an external
provisioning agent 220 to access the repository. This interface 221
allows the provisioning agent 220 to define, modify, remove, enable
or disable call control interfaces, add or remove endpoint
subscriptions, and query parameters or service states of a call
control interface or endpoint.
At system initialisation, the configuration manager 216 retrieves
the list of provisioned call control interfaces 223 from the call
services configuration repository 214 and for each interface starts
a network interface controller 218 with the parameters of the
interface. The network interface controller 218 then proceeds to
initialise the carrier links for the interface, and attempts to
contact its call server 222. The call control interface 223 becomes
active when the call server 222 and corresponding network interface
controller 218 begin exchanging call control signals. The network
interface controller 218 notifies the configuration manager 216
when its interface becomes active.
Upon activation of a call control interface 223, the configuration
manager 216 retrieves a list of endpoint subscription information
for the interface from the call services configuration repository
214. The configuration manager 216 provides the endpoint list to
the corresponding network interface controller 218. For each
endpoint in the list, the configuration manager indicates to the
corresponding network interface controller 218 whether it should
immediately resume service to this endpoint, as per the access
pattern provisioned for the endpoint. The configuration manager
also indicates access trigger events that should be reported to the
configuration manager whenever they occur. Access trigger events
include, but are not limited to, failure of the call server or
intervening transport network, transport network congestion, and
commands entered by the subscriber at the endpoint. Such command
invocations may consist of strings of dialled digits or other
inputs from the subscriber.
Depending on the call control protocol in effect on an interface
223, the network interface controller performs different functions
that may include any combination of the following. It notifies the
call server 222 with any change in the operational state of an
endpoint that subscribes to its call services, for example whether
it is in or out of service. It signals to the call server 222 any
endpoint event requested by the call server 222, or any endpoint
event whose notification is designated as mandatory by the call
control protocol. Such endpoint events include handsets being taken
off hook or being put on hook, buttons being pressed and released,
and the like. Further, it signals the line supervisor 212 for
allocating and configuring line termination units 202, as required
to perform the call services requested from the call server 222.
The network interface controller further establishes and removes
connections in the media switch 204 between line terminations units
202 and link adapters 208 for performing call services as directed
by the associated call server 222.
The line supervisor 212 is coupled via the endpoint control
interfaces 211 to every line termination unit 202 and provides the
functions necessary for network interface controllers to direct
line terminations and endpoints to implement call services. This
includes, without being limited to, the following functions.
Registering which of the network interface controllers 218 require
notification of an endpoint's events. Signaling to the registered
network interface controllers 218 any change in the operational
state of an endpoint or its line termination unit 202, for example
whether it is in or out of service. Signaling endpoint events, as
described above, to the registered network interface controllers
218. Reporting to the registered network interface controllers 218
the detection of audio signals injected in the media stream by or
through the endpoint towards the access device such as keypad
input, modem or fax tones. Reporting to the registered network
interface controllers 218 the detection of audio signals injected
by or through the network towards the endpoint, such as ringing,
alerting, recording, busy or "out-of-order" tones and the like.
Controlling elements of an endpoint's user interface through a line
termination unit. This includes activating an audible signal,
displaying a message, lighting or flashing a lamp, playing a tone
or pre-recorded message, and the like. The line supervisor also
configures and activates or deactivates media processing functions
in an endpoint or its line termination unit for the purpose of
connecting or disconnecting a call.
The network interface controller notifies the configuration manager
whenever it observes one of the requested access trigger events.
The configuration manager then consults the, access pattern of the
endpoint for which the event occurred, and modifies its access
association accordingly. To modify the access association of an
endpoint, the configuration manager notifies the current network
interface controller to suspend service to the endpoint. The
configuration manager then notifies the new network interface
controller to resume service to the endpoint, in effect to
gracefully take over control of the endpoint, and thus transferring
the endpoint to a different call server.
Thus it can be seen that the access device architecture described
herein provides a flexible system for allowing subscriber loops to
migrate gracefully between networks on a line-by-line basis. That
is, each line can be independently provisioned by either the user
or a system operation for providing a connection to a desired
network. For example, if a subscriber receives service on a TDM
network but wishes to change to a packet based system, the
subscriber can change the service simply by issuing one of the
predefined trigger events, such as dialling a predefined sequence.
Alternately, the subscriber can contact a system operator who can
program the transition to occur on a call server.
Yet further, it can be seen that the access device architecture
described herein provides a flexible system for allowing subscriber
loops to migrate gracefully between networks dynamically, on a
call-by-call basis. That is, each line can be independently
provisioned either automatically or by the user for providing a
connection to a desired network. For example, data modem calls can
be automatically detected and routed over the packet network to
reduce the load on the TDM network. In another example, subscribers
are able to switch to a different call service provider to take
advantage of lower rates. In yet another example, a subscriber line
is automatically switched to a different transport network upon
failure or congestion of their usual network. These and other
embodiments will become apparent to a person skilled in the art.
Thus it can be seem that the invention enables the graceful
migration of voice services from legacy equipment to a
next-generation network.
Although the invention has been described with reference to certain
specific embodiments, various modifications thereof will be
apparent to those skilled in the art without departing from the
spirit and scope of the invention as outlined in the claims
appended hereto.
* * * * *